Control for dual engine vehicles



May 2l, 1963 L. J. WOLF CONTROL FOR DUAL ENGINE VEHICLES 5 Sheets-Sheet 1 Original Filed June 13, 1956 mdvlw'sh Lrm. unit May 21, 1963 1 .J. WOLF CONTROL FOR DUAL ENGINE VEHICLES 3 Sheets-Sheet 2 Original Filed June 15, 1956 MPSQE, l

THHN5M/55/0N calma vAwum vnLvE i, MHNUHL CONTROL VHLUUM VHLVE May 21, 1963 l.. J. WOLF 3,090,458

CONTROL FOR DUAL ENGINE VEHICLES Original Filed June 13, 1956 5 Sheets-Sheet 3 FEST IDLE 0R N FIR 5 T NUTOMHTI UFF MHNUHL CONTROL ENG/NE DHH/EN VHCUUM VHL VE VHCUUM PUMP 83 |wncuum aulnay 86 87 V 94 85 i OPEN THRoTTUi E k 86 az 2 EXHNUST Lagaf fwd/1.

United States Patent O 3,090,458 CONTROL FOR DUAL ENGINE VEEHCLES Lloyd J. Wolf, 4580 Bordeaux St., Dallas, Tex. Original application June 13, 1956, Ser. No. 591,183, now Patent No. 3,027,962, dated Apr. 3, 1962. Divided and this application Nov. 15, 1961, Ser. No. 152,517

18 Claims. (Cl. ISO- 14) My invention relates to motor vehicles and is concerned primarily with providing an additional engine whose control is related to the speed of its propelling connections without any necessity for synchronizing both engines.

The invention is applicable to motor vehicles generally and will be described in one instance as applied to a tractor-trailer vehicle in lwhich the additional engine is mounted on the trailer, and in other instances by showings of the same concept in relation to a motor vehicle of the non-trailer type, such as ordinary trucks and buses which yare normally equipped with single engines.

In the usual vehicle of the tractor-trailer type, the entire power plant is mounted on the tractor and, since the engine and transmission must be sized to move the dead load of the tractor and trailer plus the pay load on the trailer, the tracto-r must be designed accordingly to transmit the whole trac-tive effort to the vehicle. This arrangement requires a heavy construction in the tractor with a corresponding reduction in the amount of the pay load on the trailer.

Moreover, with such a vehicle, diculty is experienced in climbing steep grades and it is necessary to provide the tractor transmission with a relatively large number of speed ratios to negotiate varying road conditions Vas well as those encountered in cross-country movements, such as in pipe laying operations. At best, this arrangement provides for crawling movements in hilly country and owing to the absence of any tractive eort by the trailer wheels, movements across unimproved ground frequently necessitate the use `of an additional tractor. Single engined buses and trucks are also characterized by the same operating ditiiculties.

Attempts to solve this problem have usually consisted in mounting an additional engine on the trailer, `or on the bus or truck, and conditioning both engines for synchronization through connection to common accelerator and clutch pedals, by arranging both transmissions to -run at the same speed, or a combination of these factors. =In the tirst arrangement, each time that a gear shift is made in the tractor Vand trailer transmissions, the accompanying movements of the accelerator and clutch pedals interrupts power iiow from the tractor and trailer engines simultaneously. The vehicle therefore loses headway and it then climbing a hill, the power interruption occurs at a time when sustained power ow is most needed. Substantially the same result occurs where the tractor and trailer transmissions are arranged for synchronization since both of these units would be shifted together with consequent interruption of power iiow from both engines.

The traverse of steep grades and poor acceleration also present serious problems in the operation of single engine trucks and buses, particularly where it is important to meet tight schedule requirements.

It is therefore the principal object of my invention to provide a motor Vehicle having a main or primary engine and an additional or booster engine whose throttle system is vacuum operated and responsive to the speed of its propelling connections,

A fur-ther object is to provide a tractor-trailer vehicle in which power distribution is effected by mounting au engine on the tractor land an independently controlled engine on :the trailer which is available as required.

ICC

A further object is to provide a motor vehicle as set forth above in which the additional power plant includes an automatic transmission having a hydrauiic coupling or a hydraulic torque converter and in which power ilow through the transmission is automatically -responsive to a predetermined speed of its propelling connection to the vehicle axle, being interrupted labove and restored below this speed.

A further object is to provide in a motor vehicle a vacuum system for automatically controlling the position of the throttle valve of the additional or booster engine in response to the speed of its propelling connections wherein the valve is shifted from fuli or partially open to idling position when the vehicle speed exceeds a predetermined value and power ow between the booste-r engine and axle ofthe vehicle or trailer, as the case may be, is interrupted and returned automatically to full or partially open position determined by the speed of the propelling connections below the predetermined value when the polwer connection is resumed.

A further object is to provide a motor vehicle in which the transmission is `of the Dynao or Hydramatic type, or generally a transmission including a hydraulic coupling or ta hydraulic torque co-nverter and constant mesh or clash gears in which provision is made for automatically varying the speed ratios therethrough in re' sponse to the speed of the propelling connections.

A further object is to provide a tractor-trailer vehicle of the character indicated in which provision is made for speed ratios additional to those furnished by the automatic transmission on the trailer through a multispeed, rear axle whose gear settings can be selectively controlled by the driver and including a neutral position to prevent driving of the transmission when the trailer is towed.

A fur-ther object is to provide a tractor-trailer vehicle in which the trailer is self-propelled through an engine, a transmission land -a multispeed, rear laxle wherein the transmission and axle are simultaneously and automatically conditioned for power transmission below a predetermined speed of the propelling connections and for neutral above this speed, the shit from one condition to another in each direction being responsive to the speed of the propelling connections.

A further object is to provide a tractor-trailer vehicle in which the trailer includes a power plant including a transmission of the Dynao or Hydramatic type and a single speed rear axle and wherein provision is made for preventing reverse drive through the transmission when the trailer is towed.

This application is a division of my copending `applic-ation, Ser. No. 591,183, ijled June 13, 1956, now Patent No. 3,027,962, which in turn was a continuation-impart of my now abandoned application, Ser. No. 187,769, filed September 30, 1950,

ln the drawings:

FIG. l is a side elevation of a tractor-trailer vehicle embodying the invention in which the trailer includes a multispeed, rear axle.

FIG. 2 is a schematic view showing the relation of the traiter engine throttle, transmission and rear axle speed controls for the vehicle shown in FIG. 1.

FIG. 3 is an enlarged, fragmentary and diagrammatic view showing the relation of the vacuum control elements for determining the position of the trailer engine throttle valve as viewed in FIG. 2, the vacuum control valves fbeing shown in positions corresponding to the idling position of the throttle valve.

FIGS. 4 and 5 are sectional views of the transmission control vacuum valve in FIG. 3 in positions determined by the low and driving ranges of the transmission, respectively, and in each of which positions, the manual control vacuum valve may be rocked to provide any desired opening of the trailer engine throttle valve beyond idling.

FIG. 6 is an enlarged, fragmentary and sectional elevation of the manual control vacuum valve in FIG. 3 in approximately iirst automatic position, i.e., a position such that the vacuum system iirst begins automatic functioning to elfect opening of the throttle valve beyond idling position.

FIG. 7 is an enlarged, sectional view of the axle gear selector valve taken along a plane parallel to that in which the valve is shown in FIG. 2.

FIG. 8 is a sectional elevation of an overrunning clutch connector which may be interposed between the transmission and rear axle of the trailer where the axle includes only a single speed.

FIG. 9 is a schematic view showing the application of the invention to a normally single engined, non-trailer vehicle, Isuch as a truck or bus.

The trailer transmission includes a hydraulic coupling or a hydraulic torque converter and devices of this type which are suitable are those marketed under the trade marks Dynailo and Hydramatic in which t-he gears are in constant mesh and change of speed rati-os from low to high is -fully automatic. Also suitable is the well known four speed transmission in which the gears are always in mesh, but which is not fully automatic through the four speeds. VAn automatic shift from rst to second speed, constituting one range, is effected 'by a vacuum system which becomes operative when the driver lifts his footfrom the accelerator pedal, but a shift from second to lthird speed is manually controlled. This transmission has a neutral position. A fourth alternative is a modification of the last noted transmission wherein the gear arrangement is of the clash gear type but controlled as indicated to provide low and driving ranges.

Referring to the drawings, FlGS. l to 7, inclusive, illustrate a tractor-trailer vehicle which is characterized by automatic throttle control of the Vtrailer engine, a speed controlled selection of the low and driving ranges of the trailer transmission, and a multispeed ratio in the trailer rear axle.

Referring to FIG. l, the numeral l designates the modiiied vehicle comprising a tractor 11 and a trailer 12. The tractor includes the usual engine Vl?) and transmission 14 which are controlled in the customary manner and connected through a propeller shaft 15 to the tractor rear axler16.

The forward end of the trailer 12 is coupled to the rear end of the tractor in the usual manner and the former may be of any conventional type except for the power plant, transmission, rear axle and the controls Vtherefor as presently described. Suitably carried on the under side of the trailer 12 is an internal combustion engine l17 which is connected to an automatic transmission having a low and a driving range, such as present commercial forms of the Dynaiio and Hydramatic transmissions. For purpose of illustration, it will be assumed that the trailer is equipped with a Dynao transmission' and that the trailer engine is of the gasoline type. The output end of the transmission 18 connects through a propeller shaft 19 to the trailer driving rear axle 2t) which will be regarded as Vof the two speed type and will be hereinafter described. The controls for the parts noted above are schematically illustrated in FIG. 2 to which reference will now be made.

In this figure, all parts to the left of the line A--A are carried by the tractor 11 and those to the right -by the trailer 12. A battery 21 has one terminal 21a grounded while the other terminal 2lb connects by a wire 22 with wires 23 and 24 which in turn respectively connect with one side of so-called microswitches 25 and 26 of vusual construction. The battery is generally `any source of electrical power and its voltage is maintained in the conventional way by a generator (not shown) which is driven by the tractor engine y13. The other side of the switch 25 connects by a wire 27 with one side of the coil of a low range solenoid 28 and the opposite end of this coil connects by a wire 29 with one terminal of a transmission switch 30 whose other terminal connects through a wire 31 and main switch 32 with ground. The other side of the microswitch 26 connects by a wire 53 with one end of the coil of a driving range solenoid 34 whose opposite end connects by a wire 35 with the wire 29 and hence with the switch 30.

The microswitches 25 and 26 include the usual plungers 36 and 37, respectively, whose movement inward of the switches closes the same and this closure is maintained for a predetermined time when the plungers move outwardly, the plungers being biased outwardly towards open positions by parts of the switch structure. Switches of this type are generally characterized Iby a snap action and the plungers by short movements and are well known in the art, a typical arrangement being shown in U.S. Letters Patent No. 1,960,020, dated May 22, i934. The plungers 36 and 37 cooperate respectively with screws 38 and 39 mounted on a rock arm d forming part of a typical speed responsive governor 41, only shown diagrammatically in FIG. 2. The internal construction of the governor is such that, as the speed of the governor shaft 42 increases, the arm 4i) rocks clockwise and, upon a decrease in speed, the arm moves towards the position shown in FIG. 2. The governor shaft 42 is driven from the tractor propeller shaft 15 by means of a belt-pulley connection designated generally by the numeral 43.

The solenoids 28 and 34 are utilized to condition the transmission lli for its forward, low and driving ranges, respectively, and the means for accomplishing this result will now be described. The core 44 of the solenoid 2S is connected by a link 45 with the free end of a transmission gear selector arm 46 which is carried by the transmission 18 and connected internally thereof in the well known manner to determine neutral and forward drive through the transmission. The core 47 of the solenoid 34 is also connected to the arm 46 through a link 4:8 radially inward of the connection of the link 45 thereto, but one end of the link i8 carries a pin 49 which operates in an elongated slot 5S in the arm 46 for .a purpose presently explained and the stroke of the core 47 is less than that of the core 44. The arm 46 is biased to the neutral position indicated by the numeral 52 in FIG. 2 by a spring 51 whose opposite ends are respectively connected to the arm and a convenient part of the transmission 18.

From. the above, it will be apparent that when the switches 30 and 32 are closed and the rock arm 40 is either in the position shown in FIG. 2 or in a slightly rocked position, as determined by the speed of the propeller shaft 15, the solenoids 28 and 34 are energized to thereby rock the arm 46 to the low range position of the transmission 18, indicated by the numeral 53 in PIG. 2, the solenoid 2S performing the primary duty in this connection by reason of the longer stroke of its core 44 and the .pin-slot or lost motion connection of the core 47 to the arm i6 enabling the latter to override the pin 49.

The screws 38 and 39 are adjusted in relation to the strokes of the plungers 36 and 37, respectively, and the movements of the arm `46 so that as the speed of the propeller shaft 15 increases and the arm 40 rocks in a clockwise direction, the screw 38 rst breaks engagement with the plunger 36 which thereby moves to an open position and interrupts the circuit through the solenoid 28. The energization of the solenoid 34 is maintained by engagernent of the screw 39 with the plunger 37 which continues to close its circuit so that the return of the transmission gear selector arm 46 under the pull of the spring 51 is limited to the driving range position indicated by the numeral 54 in FIG. 2. When the speed of the propeller shaft l5 has reached the top regulating speed as determined bythe settings of the governor 41 and screw 39, the further movement of the arm d0 separates the plunger 37 and screw 39, thus opening the switch 26, deenergizing the solenoid 34 and permitting the arm 46 to return to neutral position 52 when power ow through the transmission ceases. When the speed of the propeller shaft 15 drops below the top regulating speed, the screw 39 rst engages the plunger 37 to condition the transmission 1S for its driving range through the solenoid 34 and if the propeller shaft speed drops further to a suflicient extent, the screw 38 engages the plunger 36 and conditions the transmission 18 for its low range through the solenoid.

Advantage is taken of the propeller shaft speed responsive movements of the arm 46 to provide an automatic positioning of the trailer engine throttle valve through a vacuum system which will now be described (see FIGS. 'i to 6, inclusive). yIn this connection, it will be understood that, since the speed of the propeller shaft 15 always bears a factorial relation to the speed of the associated axle, the speed of the shaft 15 bears the same relation to the speed of the vehicle under normal, non-slipping traction conditions.

The opposite ends of a link 55 are respectively connected to the arm 46 and to one end of an arm 56 whose opposite end connects with a rotor 57 (see FIGS. 3 and 4) forming part of a transmission control vacuum valve 58 that includes a casing 59 and a cylindrical chamber 6i) within which the rotor 57 rocks. T'ne rotor 57 includes a partiadiametral pocket 61 which is open at one end and against the base thereof seats a spring 62 which biases a ball 63 into contact with the annular wall of the chamber 60. Recessed in the annular face of the rotor 57 is a parti-annular channel 64 whose length will be presently established. The chamber 60 includes a plurality of ports circumferentially spaced therearound, specifically ports 65, 66, 67 and 63. The port 65 communicates through an exhaust passage 69 in the casing 59 with the atmosphere, while the ports 66, 67 and 68 communicate, respectively, with the ends of hoses 70, 71 and 72, also mounted in the casing 59.

The other end of hose 70y connects with -a vacuum pump 73 of convention-al type suitably driven by the trailer engine 17 so that its capacity varies with the speed of this engine. The other end of hose 71 connects with the outer end of a passage 74 (see FIG. 3) that extends through the wall of a `casing 75 forming part of a manual control vacuum Valve 76 located in the tractor cab, the inner end of the passage 74 terminating in a port 77. The casing 75 also includes a vent pass-age 78 extending through the wall thereof and spaced clockwise from the passage 74. Rockable within the casing 75 is a cylindrical rotor 79 which is actuated by an external handle 80 yand which includes in the annular surface thereof a parti-annular channel 81 that, inthe off position o-f the handle 80 shown in FIG. 3, provides communication between the vent 78 and the passage 74 and thus with the hose 71. The other end of hose '72 communicates with one end of a vacuum cylinder 82 in which is reciprocable a piston S3 that is biased against an internal shoulder 84 at the opposite end of the `cylinder by a spring 85. On the other side of the piston 8-3 from the spring 85 is a chamber 86 which `communicates with the atmosphere through a port 87. The piston 83 is attached to one end of a rod forming part of a linkage, generally indicated by the numeral 88, whose opposite end connects with an arm S9 (see FIG. l) that is attached to a throttle valve 90 in the carburetor 91 of the trailer engine. Movements of the linkage 88 towards the left, as viewed in FIG. 3, shi-ft the throttle valve 90 in an opening direction, this valve being shown in idling position in FIG. 1.

Referring .to FIG. 3, it will be noted that, with the parts in the positions shown, i.e., with the engine 13 idling and the 4arm 56 shifted to the idle position by the arm 46 so that the trailer engine is not transmitting power to the axle 20, the position of the valve rotor 57 is such that 4the ball 63 masks the port 66, thus disconnecting the vacuum pump 73 from the valve 58, and that the portion ofthe cylinder 82 to the `left of the piston 83 is at atmospheric pressure by reason of the fact that the hose 72 communicates through the port 68, channel 64, port 65 and passage 69 with the atmosphere. In other words, the length of the channel 64 is such that, with the rotor 57 in the position shown in FIG. 3, it connects the ports 65, `68 and 67, but ends short o-f the port 66. The spring therefore holds the piston 83 fin the position shown which corresponds to the idling position of the throttle valve 90. Also with the handle 80` in the position shown, atmospheric pressure exists in the hose 71 since the interior of the latter communicates with the atmosphere through the passage 74, pont 77 which is fully open, channel `81 and Vent 78.

In describing the operation of the vehicle shown in FIG. l so far as described, i-t will rst be assumed that the vehicle is at rest with 4the tractor and trailer engines 13 land 17 idling, respectively, and hence the vacuum pump 73 operating, each of these engines having been started in the conventional manner. At this time, the switches 30 and 32 Aare open (see FIG. 2), the -governor arm 40 is in the retracted position shown so that the microswitches 25 and 26 `.are closed, and since the solenoids 28 and 34 are deenergized by reason of the open switches 30 and 32, the `gear selector arm 46 is in the neutral position shown. Further, the several parts of the vacuum system occupy the relative positions shown in FIG. 3 in which the vacuum pump 73 is cut off from the cylinder 82, by the ball 63.

The driver starts the vehicle moving by connecting the tractor engine 13 to the propeller shaft 15 through the usual clutch (not shown) and the transmission 14 in the conventional manner and either before, after, or simulftaneous therewith, he closes the switches 30 and 32 to thereby energize the solenoids 28l and '34 and rock the gear selector arm 46 to the low range position 53 (see FIG. 2). At the same time, the connected arm 56 moves to the position shown in FIG. 4 in which the rotor 57 masks the exhaust port 65 and the hall 63 luncovers the port `66. The vacuum pump 73 then connects through the channel 64 with the hoses 72 and 71 and therefore respectively with the cylinder 82 and the manual valve 76. However, with the latter in the position shown in FIG. 3, i.e., with the hose 71 connected through the fully open port 77 to the atmosphere through the vent 78, the pump 73 is incapable of establishing sufficient vacuum to the left of or behind the piston 83 so that atmospheric pressure acting through the port 87 can move the piston 83 and hence the linkage 88 in a direction to further open the throttle valve 96.

Preferably, the manual valve rotor 79 is rocked clockwise to the approximate position shown in FIG. 6, before, after or simultaneously with the closing of the switches 3i) and 32. The rotor 79 then partially masks the port 77 `and reduces the air iiow through Ithe hose 71 to an extent that enables suflicient vacuum to be established behind the piston .to shift the `throttle valve to what is known in the a-rt as a fast idle position and which will be regarded for present purposes as the rst automatic position. This term will be subsequentlyr explained. The rotor 79 can be held in this position in any approved manner which does not interfere with a further clockwise movement of the rotor. The first automatic position of the rotor 79 shown in FIG. 6 is diagrammatic only as it will be apparent that the actual position will depend upon the sizing of the related ports and pas-sages and the capacity of the pump at the trailer engine speed in question.

It will be obvious that, with the trailer engine idling fast, a further clockwise movement of the rotor 79 effects a further throttling of air iiow through the hose 71, a higher vacuum in the cylinder 82 and hence a further opening of the throttle valve 96 which increases the speed of the engine. When the rotor 79 completely masks the port 77, the throttle valve 96 is fully open. The handle 80 can be located in any position between fast idle and full open positions of the throttle valve 90 depending nary idling position.

7 upon theY power required of the trailer engine and left there, even when the trailer engine cuts out for reasons presently explained.

As the vehicle increases in speed, the governor arm 40 moves clockwise and at a speed determined by the adjustment of the screw 3S, the microswitch 2S opens while the screw 39 maintains closure of the microswitch 26. Accordingly, the solenoid 28 is deenergized and the spring 51 returns the gear selector arm 46 to the driving range position 54 shown in FIG. 2 as determined by the pin 49 which is held in this position by the stili energized solenoid 34.

Accompanying the shift of the arm 46 to position 54 is a rocking of the arm 56 to the position shown in FIG. 5 and while the rotor 57 rotates clockwise, it still will mask the exhaust port 65 and leaves the ports 66, 67 and 68 in communication with each other and with the vacuum pump 73. VHence, positions of the throttle valve 90 can be regulated by the valve 76 in the manner described above to provide any desired speed ratio between the tractor and trailer engines, each of which assumes its share of the total load without either engine pushing the other.

If with the arm 46 in the driving range position, the speed of the Vehicle drops suiiiciently to cause the governor arm 40 to rock counterclockwise and close the microswitch 25, such as when climbing a hill, the arm 46 is shifted to the low range position 53, thustaking advantage of the easier speed ratio in the transmission 18. Whether or not the shift to the low range position will require a different position of the throttle valve Sil will depend upon the judgment of the driver in relation to the road conditions and the total power available. It may be advantageous, particularly if the vehicle speed continues to fall, to select a different gear ratio in the tractor transmission 14. During this gear shift, power ow from the tractor engine 13 to the tractor rear axle 16 is interrupted and an important feature of the invention is that, during this shift, power dow to the trailer rear axle is maintained so that very little change in the headway of the vehicle occurs.

As already noted, the governor 41 and screw 39* are adjusted so that at some predetermined or top regulating speed of the propeller shaft 15, the governor arm 40 rocks clockwise sufficiently to open the microswitch 26 and deenergize the solenoid 34, the microswitch 25 being already open at that instant as described above. This action will occur with the gear selector arm 46 in driving range position S4 which is accordingly shifted to neutral position 52 by the spring 51 so that the trailer engine 17 is disconnected from the trailer propeller shaft 19. If the speed of the propeller shaft 15 falls below the top regulating speed, the arm 46 is restored to driving range position 54 and power ow from the trailer engine is resumed.

A further important advantage is that when the transmission 18 shifts from driving range to neutral at the top regulating speed of the propeller shaft 1S, it is unnecessary to change the position of the handle Si? for the purpose of moving the throttle to fast or ordinary idling position. The handle 80 is left in whatever position it occupied when power ow from the trailer engine was interrupted and the shifting of the arm 56 by the arm 46 to the position shown in FIG. 3 causes the ball 63 to close the port 66 and hence interrupt the influence of the vacuum pump 73 while, at the same time, the exhaust port 65 is unmasked and atmospheric pressure is reestablished in the Vcylinder `82 to the left of the piston 83 so that the latter moves to the right and through the linkage 83 shifts the n throttle valve 90 to ordinary idling as distinguished from fast idling position. Accordingly, the trailer engine 17 is prevented from racing when the transmission 18 is shifted to neutral as would otherwise occur if it was necessary to rock the handle S to shift the throttle valve 99 to ordi- My improved arrangement therefore eliminates driver error and forgetfulness.

.may include two speeds.

When the vehicle speed falls below the top regulating speed, the transmission is immediately restored to driving range and the transmission control vacuum valve S8 assumes the position shown in FIG. 5 so that the vacuum pump 73 again becomes effective. Hence, since the valve 76 is in the same position which is occupied when the trailer engine cut out, i.e., in a position wholly or partially throttling air ow through the hose 71, the ensuing creation of a vacuum condition in the cylinder 82 quickly shifts the throttle valve 99 to the position occupied when the trailer engine cut out. -In this connection, it will be noted that when the trailer engine cuts in, its throttle valve is in ordinary idling position, but the trailer engine immediately speeds up by reason of its connection to the trailer rear axle 20 and since the vacuum pump 73 is driven by this engine, the vacuum established thereby rapidly opens the throttle valve 99 to a position corresponding to the engine speed and as determined by the setting of the manual valve 76.

This quick opening movement of the throttle valve 99 under the conditions just stated is primarily due to the slip connection between the trailer engine and transmission provided by the hydraulic coupling or torque converter as the case may be. Hence, when power ow through the transmission is resumed due to vehicle speed falling below the top regulating speed and communication is reestablished between the vacuum pump 73 and the cylinder 82 with the rotor 79 in at least the fast idling position shown in FIG. 6, the fact that the trailer engine is momentarily not under load by reason of the slip connection to the transmission enables the engine to quickly increase its speed to a point suiicient to take up the load.

`From the foregoing, it will be apparent that the term first automatic position of the valve 76 means that in any position of the valve rotor 7 9 between the iirst automatic position as shown in lFIG. 6 and a position in which the rotor masks the port 77, the throttle -valve 90, when the trailer engine cuts in, will lbe automatically returned to the position which it occupied when the trailer engine cuts out without any necessity for moving the handle `80.

In the case of an emergency stop, if the Vehicle speed when the brakes are applied is above the top regulating speed and hence with the trailer engine idling, the trailer transmission cuts in when the speed falls suciently and while the throttle valve gti momentarily opens for reasons noted above, it quickly returns to idle position because of the decreasing vacuum available as the speed of the engine driven vacuum pump 73 falls.

Normally, the vehicle speed represents the combined efforts of both engines, with the trailer engine responsive thereto and not only cutting in and out as this speed varies -below and above a top regulating speed, but with the trailer power unit having the further capacity, also responsive to vehicle speed, of changing speed ratios in the associated transmission as vehicle speed moves up and down. Even when the yvehicle speed is a function only of the tractor engine, the controls for the trailer engine are always tied to vehicle speed by reason of the 4governor connection to the propeller shaft of the tractor. Further, throttle valve movements of the trailer engine, for any given position of the handle `80, are fully automatic between idling and whatever position was originally determined -by the handle as the trailer engine cuts in and out.

Where it is desirable to have speed ratios additional to those provided by the transmission 18, the rear axle Zt) In FIG. l, the trailer 12 is shown with a tandem rear axle construction and while either axle may be employed as the driving axle, it will be assumed that the forward axle 2t) performs this function. A diagrammatic arrangement of this construction and the controls therefor are also illustrated in FIG. 2 which have been conveniently associated with the other mechanism in this gure already described.

Referring toFIG. 2, the fixed terminal of an axle switch 92, located in the tractor cab, connects by a wire 93 lwith one terminal of the main switch 32. The switch 92 is selectively swingable between contacts 94 and 95, the former connecting by a wire 96 with one end of the coil of a low speed solenoid 97 Whose opposite end connects by a wire 98 with the wire 33 and hence with the microswitch 26 whose closure energizes the driving range solenoid 34. The contact 95 connects by a wire 99 with one end of the coil of a high speed solenoid 100 Whose opposite end connects by a wire `101 with the wire 98 and therefore with the microswitch 26. Accordingly, it Will Ibe understood that the solenoids 97 and 100 are never simultaneously energized, but are selected depending upon the gear ratio desired in the rear axle.

The solenoid 97 includes the usual core 102 which is connected at one end by a link f103 -with the free end of a rockable axle gear selector arm `104- that is biased in the neutral or of -position k105 shown by a spring A105. The solenoid 100 includes a core 107 whose outer end connects with one end of a link 108 Whose opposite end carries a pin 109 that operates in an elongated slot 110 lformed in the arm -104 radially inward of the connection of the link 103 thereto. The core 102 has a longer stroke than the core 107, the former when the associated coil is energized, shifting the arm 104 to low gear position 111 while the latter, when the coil of the solenoid :100 is energized, shifts or holds the arm to or in the high gear position 112, the slot or lost motion connection 110 permitting overriding of the pin 109 when the arm 104 is rocked to position 111.

The rocking of the arm 104 determines the position of an axle gear selector valve 113 which controls the admission and exhaust of air under pressure to and from a double acting piston mechanism presently described. Referring to FIG. 7 which more particularly shows the valve construction, it comprises a casing 114 having a cylindrical chamber 115 in which rocks a similarly shaped rotor -116 to which the inner end of the arm 104 is connected. Aligned, radial passages 117 and 11S yextend through the rotor 1116 with their outer ends terminating at the annular surface thereof and -their inner ends communicating with a passage 119 extending axially of the rotor 116. One end of the passage y1119 communicates through the casing 114 with a hose -120 which in turn connects with a source of air under pressure, such as a tank 121 (see FIG. l), that is maintained at a predetermined pressure by conventional means not shown. Air under pressure is therefore always present in the passages 1117 and 118.

Parti-annular, long and short channels 122 and 123 are recessed in the peripheral surface of the rotor 1116, the ends of the channel y122 terminating `adjacent the outer ends of the passages 117 and 118, all respectively, while the channel 123 is located on the opposite side of the passage 118 with one end terminating adjacent this passage and the opposite end spaced a convenient distance therefrom.

With the rotor 1116 in the position shown in FIG. 7, the channel 122 provides communication between passages 124 and 125 which extend through the casing l1'14 and respectively communicate with the atmosphere and with one end of a hose .126, while the channel 123 connects passages 127 and 128 which `also extend through the casing 114 and respectively communicate with the atmosphere and one end of a hose 129.

Referring to FIG. 2, the other ends of the hoses 126 and 129 respectively communicate with chambers 130 and 131 provided at opposite ends of a cylinder 132 in which is reciprocable a double acting piston 133 that separates the chambers and is mounted on a rod 134 that extends through one end of the cylinder and a bearing 135 spaced therefrom and forming part of a bracket 136 that is carried by the cylinder. An abutment plate 137 is fast to the lbearing 13S and a second abutment plate 138 is positioned midway between the plate 136 and the adjacent end of the cylinder 132, both plates being coaxial with the rod 134 and the plate 138 being secured to this 10 rod in any approved manner. A spring 139 encircles the the rod 134 between the plates 137 and 138 and the adjacent end of the cylinder 132. These springs are of equal strength and bias the piston 133 to the intermediate position shown which determines the neutral of the two speed axle.

Tl" he rod 134- extends through the bearing 135 for connection with one arm of a lever 141 that is pivoted on the bracket 136, the other arm of the lever being connected through a link 142 with a shiftable yoke 143 having spaced forked arms 144 and 145 which respectively engage clutch members 146 and 147 splined to a jack shaft 148 which is parallel to the rear axle 20, the arms 144 and 145 being arranged to axially shift the members 146 and 147 while permitting rotation of the latter. One end of the jack shaft 148 carries a bevel gear 149 which meshes with a bevel pinion 150 secured to the output end of the propeller shaft 19. Between the clutch members 146 and 147 are pinions 151 and 152 which are freely journaled on the jack shaft 148 and held against axial movement in any desired manner, one side of each of the pinions 151 and 152 being arranged for clutching engagement with the members 146 and 147, respectively. The pinions 151 and 152 mesh with gears 153 and 154, respectively, that are keyed to the rear axle 20, with the pinion 151 and gear 153 constituting the low gear of the axle and the pinion 152 and gear 154 forming the high gear. For the sake of clearness, the diierential gear mechanism has `been omitted.

As noted in FIG. 2, the solenoids 97 and 100 are deenergized and the valve 113 is in the position shown in FIG. 7 wherein the outer ends of the passages 117 and 118 are masked by the casing 114 and both chambers 130 and 131 are at atmospheric pressure since the former communicates through the hose 126, passage 125, channel 122 and passage 124 with the atmosphere, while the chamber communicates through the hose 129, passage 128, channel 123 and passage 127 with the atmosphere. Hence, the piston 133 is balanced in the neutral position shown 'by the springs 139 and 140 and the clutch members 146 and 147 are free of engagement with the pinions 151 and 152, respectively.

This capacity to break connection between the rear axle 20 and transmission 18 is an important feature of the invention. In automatic transmissions of the Dynalow and Hydramatic type, speed ratios are controlled by speed bands and clutches which are hydraulically actuated by liquid discharged by pumps, one being engine driven and the other being responsive to vehicle speed. Hence, when the trailer is being towed by the tractor, the ability to break connection between the trailer propeller shaft 19 and trailer rear axle 20 prevents unwanted operation of the pumps noted above and therefore possible burning out of the speed bands and clutches.

When the vehicle is placed in motion by the tractor engine 13, the switch 92 is swung to engage either the contact 94 or 95, depending upon the conditions of operation, simultaneously with or prior to the closing of the switch 30. Assuming that contact 94 is engaged, the low speed solenoid 97 is thereby energized, thus shifting the arm 104 to the low speed position 111 and rocking the valve rotor 116 counterclockwise until the outer end of the passage 117 registers with the passage 125 to thereby admit compressed air through the hose 126 to the chamber 130. At the same time, the outer end of the passage 118 is masked by the annular Wall of the chamber between the passages 127 and 128 while the channel 122 provides communication between the passages 128 and 124 so that the cylinder chamber 131 is open to the atmosphere. Accordingly, the piston 133 moves to the right, as viewed in FIG. 2, compresses the spring 139 and through the lever 141 and link 142 shifts the yoke 143 and effects engagement of the low speed pinion 151. Power connection to the rear axle 20 through the latters low speed gear is now 11 complete and the trailer engine can be accelerated in the manner described above.

As the speed of the vehicle rises, it will ordinarily be desirable to utilize the high gear of the rear axle. For this purpose, the switch 22 is moved to engage the contact 95, thus deenergizing the low speed solenoid 97 and energizing the high speed solenoid 1019 whereupon the arm 104 under the pull of the spring 1116 shifts to the high speed position 112 where it is held by the pin 169. The valve rotor 116 is thereby roc-lied clockwise to shift the outer end of the passage 113 from between the passages 127 and 128 where it was masked by the wall of the chamber 115 into registration with the passage 12d. At the same time, the outer end of the passage 117 moves out of registration with the passage 125 and communication is established through the channel 122 between passages 125 and 124. Hence, compressed air is supplied to the chamber 131 and the chamber 13u is open to the atmosphere. Accordingly, the piston 133, urged by the 'hitherto compressed spring 139 and the air pressure in the chamber 131, moves to the left and through the lever 141, link 142 and yoke 143 disengages the clutch member 146 and engages the clutch member 147 to establish drive through the high gear set comprising the pinion 152 and gear 154.

At any speed of the vehicle below the top regulating speed as delined above, and while the trailer transmission 18 is in low or driving range, either of the gear ratios in the rear axle may be selected at will to meet road conditions, thus providing a more flexible arrangement than that aorded by the transmission alone.

Another feature is the automatic shifting of the two speed rear axle to neutral when the top regulating speed of the vehicle is reached. This facility arises by reason of the tying in of the low and high speed circuits which control the selection of the rear axle speeds with the circuit which controls the driving range of the transmission 18.` At the top regulating speed, the microswitch 26 opens which not only deenergizes the driving range solenoid 34 so that the transmission gear selector arm d6 returns to neutral position 52, the low range solenoid 23 having previously beenV deenergized, all as described above, but also either the low speed solenoid 97 or the high speed solenoid 11i@ is deenergized depending upon the position of the axle switch 92 so that the rear axle structure is conditioned for neutral. Further, when the speed of the vehicle falls below the top regulating speed, the closing of the microswitch 26 simultaneously energizes the solenoid 34 and either the solenoid 97 or the solenoid 1th) to thereby restore the transmission 18 and and rear axle Ztl to power transmitting condition. In other words, the transmission and the rear axle gear sets are simultaneously and automatically conditioned for power transmission below a determined vehicle speed and simultaneously and automatically shifted to neutral above this speed without any requirements on the part of the driver.

Where the complete system as shown in FIG. 2 is employed, the switch 32 serves as a single cut-out switch whose opening interrupts all circuits and therefore provides a convenient device for quickly shifting the transmission and rear axle to neutral in the event of an emergency stop ofthe vehicle. lf an ordinary single speed, rear axle is employed, all the controls shown for the two speed, rear axle in FlG. 2 are eliminated, including the switch 32, so that the transmission switch 319 serves as the emergency cut-out. Under these conditions, it is still necessary to provide a connector between the output end of the transmission 18 and the rear axle to prevent drive from the latter through the transmission when the trailer is being towed. A suggested connector for this purpose is illustrated in FIG. 8 to which reference will now be made.

The connector, designated generallyV by the numeral 155, is interposed* between and connected to the output shaft ofthe transmission 18 and a propeller shaft 156 which in turn connects through the usual bevel gear set 157 with the rear axle 158, the dilferential gear being omitted for the sake of clearness. The connector includes a stub shaft 159 which is splined at one end for attachment to an output member of the transmission 18 and at the opposite end is counterbored at '161B to thereby form an external annular shoulder 161. The opposite ends of a tube 162 are respectively secured to the shoulder` 161 and a hub 163 which forms the inner race of an overrunning clutch, designated generally by the numeral 164i, which additionally includes rollers 1765 and an outer race 166 which is secured to one end of a tubev 167.y Internally, the same end of the tube 157 is fast in any approved manner to an intermediate shaft 168 that is journaled in suitable bearings within the counterbore V and hub 163 and in alignment with the stub shaft 159. The opposite end of the tube 167 connects through a conventional universal joint with one end of the propeller shaft 156;

When the transmission 18 is in low or driving range, power ow through the connector 155 is towards the right as viewed in FIG. S so the overrunning clutch 164 is engaged in the usual way, but when the transmission is in neutral and the trailer is being towed by the tractor, connection through the clutch 164 is broken in the usual manner. Inadvertant and unwanted operation of the pumps in the transmission 18 are therefore prevented.

In FIG. 9 is diagrammatically illustrated the application of the invention, less the two-speed, rear axle control shown in v1BIG. 2, to a typical truck, bus or similar vehicle which is usually equipped with a single engine, as distinguished from a tractor-trailer vehicle.

Engine No. l, designated by the numeral 170, indicates the usual truck engine which is connected to a transmission 1'71 that may be of the conventional, manually controlled type. The power plant comprising the engine 17) and transmission 171 corresponds to the similar tractor equipment described above.

Engine No. 2, designated by the numeral 172, indicates an additional engine whose power is available as required in response to vehicle speed and which is coupled to any of the transmissions referred to above, generally indicated by the numeral 173, Le., these transmissions would be of the type suggested for the trailer transmission. The engine 172 and transmission 173 oorrespond to the similar trailer components described above and ,would have associated therewith the throttle valve and transmission controls above described, omitting the two-speed, rear axle control shown in FIG. 2.

The output of the transmission 171 connects direct to one input side of a transfer case or mechanism 174 of conventional construction while the output of the transmission 173 may connect through the overrunning clutch connector 155 shows in iFIG. 8 with another input side fof the case 174. he common output of the case 174 connects through a propeller shaft 175 with the rear axle 176 in the usual way. Where a Dynallo or a Hydramatic transmission is employed, the connector 15'5 prevents, when power ilow from the engine 172 is interrupted above the top regulating speed, inadvertent operations of the pumps which control the actuation of the speed bands and clutches.

The operating characteristics of the arrangement shown in FG. 9 will be similar to the tractor-trailer type of vehicle. Accordingly, power flow from the additional engine 172 will be automatically established and interrupted below and above the top regulating speed of the vehicle and speed ratios in the transmission 173 will automatically vary in response to vehicle speed.

I claim:

1. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer coupled to the tractor having an engine controlled independently of the tractor engine and a transmission of the constant mesh type drivably connected to an axle of the trailer and having low and driving ranges, and means adapted to respectively condition the trailer transmission for power flow in the low and driving ranges comprising a selector arm for the trailer transmission movable between positions determining the low and driving ranges thereof, a pair of parallel, low and driving range electric circuits each including a solenoid having a core connected to the arm, a switch in each circuit biased to an open position, and means responsive to the speed of one of the axles for permitting the low range switch to open above a predetermined speed of said axle while maintaining closure of the driving range switch.

2. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer coupled to lthe tractor having an engine controlled independently of the tractor engine and a transmission drivably connected to an axle of the trailer and having low and driving ranges, and means adapted to respectively condition the trailer transmission for power ilow in the low and driving ranges comprising a selector arm for the trailer transmission movable between positions determining the low and driving ranges thereof, a pair of parallel, low and driving range, electric circuits each including a solenoid having a core connected to the arm, a switch in each circuit biased to an open position, and a pivoted arm responsive to the speed of one of the axles having a pair of adjustable, low and driving range members respectively adapted to engage the switches, the members closing both switches bel-ow a predetermined speed of said one axle in one position of the pivoted arm and the low range member permitting the low range switch to open above said speed while the driving range member maintains closure of the driving range switch in another position of the pivoted armi.

3. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer coupled to the tractor having an engine controlled independently of the tractor engine and a transmission drivably connected to an axle of the trailer and having low and driving ranges, and means adapted to respectively condition the trailer transmission Ifor power flow in the low and driving ranges comprising a pivoted selector arm for the trailer transmission movable between positions determining the low and driving ranges thereof, a pair of parallel, low and driving range electric circuits each including a solenoid having a core connected to the arm, the driving range core having a shorter stroke than the low range core and having a pin-slot connection to the selector arm inwardly of the connection of the low range core thereto, a switch lin each circuit for controlling the energization of the associated solenoid, and a member responsive to the speed of one of the axles for determining the opening and closing of each switch.

4. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine controlled independently of the tractor engine and a transmission drivably connected to an axle of the trailer and having low and driving ranges and a neutral, and means adapted to respectively condition the trailer transmission for power ow in the low and driving ranges and Afor neutral comprising a pivoted selector arm for the trailer transmission movable between positions determining the low and driving ranges and neutral thereof, a pair of parallel, low and driving range electric circuits each including a solenoid having a core connected to the selector arm, a switch in each circuit biased to an open position, a pivoted arm responsive to the speed of one of the axles having a pair of adjustable, low and driving range members respectively adapted to engage the switches, the members closing both switches below a predetermined speed of said one axle to condition the trailer transmission for low range and the pivoted arm being successively moved to a position in which the low range member is freed from the low range switch to condition the trailer transmission for driving range above said predetermined speed and to a position in which the driving range member is freed from the driving range switch to condition the trailertransmission for neutral when the trailer speed is higher than said last named speed, and means for returning the selector arm to neutral position when the driving range switch opens.

5. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, means responsive to the speed of one of the axlesv adapted to respectively condition the trailer transmission for power flow and for neutral below and above a predetermined speed of said one axle, and other means responsive to said one axle speed adapted to return the throttle valve from an original to idling position when the trailer transmission shifts to neutral and to move the throttle valve to its original position when power flow through the trailer transmission is resumed.

6. A tractoretrailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, means responsive to the speed of one of the axles adapted to respectively condition the trailer transmission for power flow and `for neutral below and above a predetermined speed of said one axle, and vacuum means adapted to return the throttle valve from an initial to idling position when the trailer transmission shifts to neutral and to move the throttle valve to the initial position when the power flow through the trailer transmission is resumed including a positive displacement vacuum pump driven by the trailer engine, and manually controlled valve means forming part of the vacuum means `for determining said initial and idling positions of the throttle valve.

7. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, means responsive to the speed of one of the axles adapted to respectively condition the trailer transmission for power ofw and for neutral below and above a predetermined speed of said one axle, and vacuum means connected to the responsive means and simultaneously operable therewith adapted to return the throttle valve from an initial to idling position when the trailer transmission shifts to neutral and to move the throttle Valve to the initial position when power iiow through the trailer transmission is resumed, and manually controlled valve means forming part of the vacuum means for determining said initial posi- -tion of the throttle valve.

8. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, means responsive to the speed of one of the axles adapted to respectively condition the trailer transmission for power liow and for neutral below and above a predetermined speed of said one axle, and a vacuum system for determining positions of the throttle valve comprising a vacuum pump driven by the trailer engine, a cylinder having a piston reciprocable therein and connected to the throttle valve, the piston being constantly subjected to atmospheric pressu`re on one side and biased on the `other side to a position determining the idling position of the throttle valve, rst valve means having an exhaust port and responsive to conditionings of the trailer transmission for power flow and neutral and shiftable between a position closing the exhaust port and connecting the pump with the biased side of the piston during periods of power iiow through the trailer transmission and a position disconnecting the pump from the cylinder and connecting the biased side of the piston to Vthe exhaust port during periods of trailer transmission neutral, and manually controlled valve means having a constantly open vent port and a passage communicating with the 1first valve means and operable -to regulate air flow from the vent port through the passage when the pump is connected to the cylinder to vary the extent of vacuum therein and the position of the throttle valve.

9. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, means responsive to the speed of lone of the axles adapted to respectively condition the trailer transmission for power flow and for neutral below and above-a predetermined speed of said one axle, and a vacuum system for determining positions of the throttle valve comprising a vacnum pump driven by the trailer engine, a cylinder having a piston reciprocable ltherein and connected to the throttle valve, the piston being constantly subjected to atmospheric pressure on one side and biased on the other side to a position determining the idle position of the throttle valv rst valve means having an exhaust 4port and connected to the responsive means and simultaneously operable therewith and shiftable between a position closing the exhaust port and connecting the pump with the biased side of the lpiston during periods of power flow through the trailer transmission and a position disconnecting the pump from the cylinder and connecting the biased side of the.

piston to the exhaust port during periods of trailer transmission neutral, and manually controlled valve means having a constantly open vent port and a passage communicating with the `first valve means and operable to regulate air flow from the vent port through the passage when the pump is connected to the cylinder to vary the extent of Vacuum therein and the position of the throttle valve.

10. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer coupled to the ytractor having an engine controlled independently of the tractor engine, a transmission having a neutral and a driving range and a rear axle having a plurality of gear ratios and a neutral, means responsive to the speed of one of the axles adapted to respectively condition the trailer transmission for power flow and for neutral below and above a predetermined speed of said one axle, means for selecting a gear ratio in the -trailer rear axle, and means responsive to said one axle speed arranged to condition the rear axle for neutral when the trailer transmission is in neutral and to restore the rear axle to the selected gear ratio when the -trailer transmission is conditioned for power flow.

l1. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer coupled to the tractor having an engine controlled independently of the tractor engine, a transmission having a neutral and a driving range and a rear axle having ya plurality of gear ratios and a neutral, means adapted to respectively condition the trailer transmission for power dow .and for neutral below and above a predetermined speed of one of the axles comprising a first selector arm for the trailer transmission movable between positions determining the driving range and neutral thereof, an electric circuit including a first solenoid having a core connected to the rst selector arm, a switch for controlling the energization of the first solenoid to move the first selector arm to driving range position, and a member responsive to said one axle speed for determining the opening and closing of the switch, means for selecting a gear ratio in the rear axle comprising a plurality of solenoids in parallel with each other and forming a part of the electric circuit, the last named solenoids as a group being in parallel with the rst named solenoid, means for selectively energizing one of the plurality of solenoids, and means common. to the last named solenoids for engaging the selected gear ratio corresponding to one of the last named solenoids, `and means including the member arranged to condition the rear axle for neutral when the trailer transmission is in neutral and to restore the rear axle to a selected gear ratio when the trailer transmission is conditioned for power flow.

l2. A self-propelled trailer for a vehicle of the tractortrailer type having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and including a hydraulic power circuit means and having a driving range and a neutral, remote means responsive to the speed of one of the vehicle axles adapted to respectively condition the trailer transmission for power llow and for neutral below and above a predetermined speed of said vehicle axle, and vacuum means adapted to return the throttle valve to idling position when Vthe transmission shifts to neutral and to move the throttle to an original position when power flow through the transmission is resumed including a positive displacement vacuum pump driven by the engine and manually controlled valve means forming part of the vacuum means for determining said original and idling positions of the throttle valve.

13. In a motor vehicle, the combination of a first engine, a transmission connected thereto, a second engine, a throttle valve for the second engine, a second transmission connected to the second engine having a driving range and a neutral and. including a hydraulic power circuit means, each transmission being drivably connected to an associated axle of therrvehicle, means responsive to the speed of one of the axles adapted to respectively condition the second transmission for power flow and for neutral below and above a predetermined speed of said one axle, and other means responsive to the speed of said one axle adapted to return the throttle valve to idling position when the second transmission shifts to neutral and to move the throttle valve to its original position when the power flow through the second transmission is resumed.

14. In a motor vehicle, the combination of a lirst engine, a transmission connected thereto, a second engine, a throttle valve for the second engine, a second transmission connected to the second engi-ne, having a driving range and a neutral and including a hydraulic power circuit means, each transmissionrbeing drivably connected to an associated axle of the vehicle, means responsive to the speed of one of the axles adapted to respectively condition the second transmission for power flow and for neutral below and above a predetermined speed of said one axle, and vacuum means connected to the responsive means and simultaneously operable therewith adapted to return the throttle valve from an initial to idling position when the second transmission shifts to neutral and to move the throttle valve to the initial position when power flow through the second transmission is resumed, and manually controlled valve means forming part of the vacuum means for determining said initial position of the throttle valve.

l5. In a motor vehicle, the combination of a first engine, a transmission connected thereto, ya second engine, a throttle valve for the second engine, a second transmission connected to the second engine having a driving range and a neutral, each transmission being drivably connected to axle means of the vehicle, means responsive to the speed or the axle means adapted :to respectively condition the second transmission for power ow and for neutral below and above a predetermined speed of the axle means, and a vacuum system for determining posiitons of the throttle valve comprising a vacuum pump driven by the second engine, a cylinder having a piston reciprocable therein and connected to the throttle valve, the piston being constantly subjected to atmospheric pressure on one side and biased on the other side toa position determining the idling position of the throttle valve, iirst valve means having an exhaust port and responsive to Conditionings of the second transmission for power ow and neutral and shiftable between a position closing the exhaust port and connecting the pump with the biased side of the piston during periods of power ow through the second transmission `and a position disconnecting the pump from the cylinder and connecting the biased side of the piston to the exhaust port during periods of second transmission neutral, and manually controlled valve means having a constantly open vent port and a passage communicating with the iirst valve means `and operable to regulate air flow from the vent port through the passage when the pump is connected to the cylinder to 'vary the extent of vacuum therein and the position of the throttle valve.

16. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and having a driving range and a neutral and including a hydraulic power circuit means, a selector arm movable between positions `determining power iiow through and neutral in the trailer transmission, and other means connected to the selector arm and including parts operably related to the throttle Valve for returning the latter from an original to idling position when the trailer transmission shifts to neutral and for moving the throttle valve to its original position when power flow through the trailer transmission is resumed.

17. A tractor-trailer vehicle comprising a tractor having an engine and a transmission connected to the driving axle thereof, a trailer having an engine, a throttle valve therefor and a transmission drivably connected to an axle of the trailer and having a driving range and a neutral and including a hydraulic power circuit means, a selector arm movable between positions determining power flow through and neutral in the trailer transmission, and vacuum means connected to the selector arm and simultaneously operable therewith and adapted to return the throttle valve from an initial to idling position when the trailer transmission shifts to neutral and to move the throttle valve to the initial position when power .ilow through the trailer transmission is resumed, and manually controlled valve means forming part of the vacuum means for determining said initial position of the throttle valve.

18. In a motor vehicle, the combination of a rst engine, a transmission connected thereto, a second engine, a throttle valve for the second engine, a second transmission connected to the second engine having a driving range and a neutral and including a hydraulic power circuit means, each transmission being drivably connected to axle means of the vehicle, a Iselector arm movable between positions determining power ow through and neutral in the second transmission, :and vacuum means connected to the selector arm and simultaneously operable therewith yand adapted to return the throttle valve from an initial to idling position when the second transmission shifts to neutral and to move the throttle valve to the initial position when power ow through the second transmission is resumed, and manually controlled valve means forming part of the vacuum means for determining said initial position of the throttle valve.

No references cited. 

5. A TRACTOR-TRAILER VEHICLE COMPRISING A TRACTOR HAVING AN ENGINE AND A TRANSMISSION CONNECTED TO THE DRIVING AXLE THEREOF, A TRAILER HAVING AN ENGINE, A THROTTLE VALVE THEREFOR AND A TRANSMISSION DRIVABLY CONNECTED TO AN AXLE FOR THE TRAILER AND INCLUDING A HYDRAULIC POWER CIRCUIT MEANS AND HAVING A DRIVING RANGE ND A NEUTRAL, MEANS RESPONSIVE TO THE SPEED OF ONE OF THE AXLES ADAPTED TO RESPECTIVELY CONDITION THE TRAILER TRANSMISSION FOR POWER FLOW AND FOR NEUTRAL BELOW AND ABOVE A PREDETERMINED SPEED OF SAID ONE AXLE, AND OTHER MEANS RESPONSIVE TO SAID ONE AXLE SPEED ADAPTED TO RETURN THE THROTTLE VALVE FROM AN ORIGINAL TO IDLING POSITION WHEN THE TRAILER TRANSMISSION SHIFTS TO NEUTRAL AND TO MOVE THE THROTTLE VALVE TO ITS ORIGINAL POSITION WHEN POWER FLOW THROUGH THE TRAILER TRANSMISSION IS RESUMED. 